FFmpeg/libavcodec/adxenc.c

/*
 * ADX ADPCM codecs
 * Copyright (c) 2001,2003 BERO
 *
 * This file is part of Libav.
 *
 * Libav is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * Libav is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with Libav; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "libavutil/intreadwrite.h"
#include "avcodec.h"
#include "adx.h"
#include "put_bits.h"

/**
 * @file
 * SEGA CRI adx codecs.
 *
 * Reference documents:
 * http://ku-www.ss.titech.ac.jp/~yatsushi/adx.html
 * adx2wav & wav2adx http://www.geocities.co.jp/Playtown/2004/
 */

static void adx_encode(ADXContext *c, uint8_t *adx, const int16_t *wav,
                       ADXChannelState *prev)
{
    PutBitContext pb;
    int scale;
    int i;
    int s0, s1, s2, d;
    int max = 0;
    int min = 0;
    int data[32];

    s1 = prev->s1;
    s2 = prev->s2;
    for (i = 0; i < 32; i++) {
        s0 = wav[i];
        d = ((s0 << COEFF_BITS) - c->coeff[0] * s1 - c->coeff[1] * s2) >> COEFF_BITS;
        data[i] = d;
        if (max < d)
            max = d;
        if (min > d)
            min = d;
        s2 = s1;
        s1 = s0;
    }
    prev->s1 = s1;
    prev->s2 = s2;

    if (max == 0 && min == 0) {
        memset(adx, 0, 18);
        return;
    }

    if (max / 7 > -min / 8)
        scale = max / 7;
    else
        scale = -min / 8;

    if (scale == 0)
        scale = 1;

    AV_WB16(adx, scale);

    init_put_bits(&pb, adx + 2, 16);
    for (i = 0; i < 32; i++)
        put_sbits(&pb, 4, av_clip(data[i] / scale, -8, 7));
    flush_put_bits(&pb);
}

static int adx_encode_header(AVCodecContext *avctx, uint8_t *buf, int bufsize)
{
    ADXContext *c = avctx->priv_data;

    AV_WB32(buf + 0x00, 0x80000000 | 0x20);
    AV_WB32(buf + 0x04, 0x03120400 | avctx->channels);
    AV_WB32(buf + 0x08, avctx->sample_rate);
    AV_WB32(buf + 0x0c, 0);
    AV_WB16(buf + 0x10, c->cutoff);
    AV_WB32(buf + 0x12, 0x03000000);
    AV_WB32(buf + 0x16, 0x00000000);
    AV_WB32(buf + 0x1a, 0x00000000);
    memcpy (buf + 0x1e, "(c)CRI", 6);
    return 0x20 + 4;
}

static av_cold int adx_encode_init(AVCodecContext *avctx)
{
    ADXContext *c = avctx->priv_data;

    if (avctx->channels > 2) {
        av_log(avctx, AV_LOG_ERROR, "Invalid number of channels\n");
        return AVERROR(EINVAL);
    }
    avctx->frame_size = 32;

    avctx->coded_frame = avcodec_alloc_frame();

    /* the cutoff can be adjusted, but this seems to work pretty well */
    c->cutoff = 500;
    ff_adx_calculate_coeffs(c->cutoff, avctx->sample_rate, COEFF_BITS, c->coeff);

    return 0;
}

static av_cold int adx_encode_close(AVCodecContext *avctx)
{
    av_freep(&avctx->coded_frame);
    return 0;
}

static int adx_encode_frame(AVCodecContext *avctx, uint8_t *frame,
                            int buf_size, void *data)
{
    ADXContext *c          = avctx->priv_data;
    const int16_t *samples = data;
    uint8_t *dst           = frame;
    int rest               = avctx->frame_size;

    if (!c->header_parsed) {
        int hdrsize = adx_encode_header(avctx, dst, buf_size);
        dst += hdrsize;
        c->header_parsed = 1;
    }

    if (avctx->channels == 1) {
        while (rest >= 32) {
            adx_encode(c, dst, samples, c->prev);
            dst     += 18;
            samples += 32;
            rest    -= 32;
        }
    } else {
        while (rest >= 32*2) {
            int16_t tmpbuf[32*2];
            int i;

            for (i = 0; i < 32; i++) {
                tmpbuf[i   ] = samples[i*2  ];
                tmpbuf[i+32] = samples[i*2+1];
            }

            adx_encode(c, dst,      tmpbuf,      c->prev    );
            adx_encode(c, dst + 18, tmpbuf + 32, c->prev + 1);
            dst     += 18*2;
            samples += 32*2;
            rest    -= 32*2;
        }
    }
    return dst - frame;
}

AVCodec ff_adpcm_adx_encoder = {
    .name           = "adpcm_adx",
    .type           = AVMEDIA_TYPE_AUDIO,
    .id             = CODEC_ID_ADPCM_ADX,
    .priv_data_size = sizeof(ADXContext),
    .init           = adx_encode_init,
    .encode         = adx_encode_frame,
    .close          = adx_encode_close,
    .sample_fmts    = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_S16,
                                                      AV_SAMPLE_FMT_NONE },
    .long_name      = NULL_IF_CONFIG_SMALL("SEGA CRI ADX ADPCM"),
};